Electrical system



Sept. 21 ,1926. v 1,600,316

' C. E. CAMPBELL ELECTRICAL SYSTEM ori inal Filed Oct 1919 2 Sheets-Sheet 1 Sept. '21 was; 1,600,316

(I. E. CAMPBELL ELECTRICAL SYSTEM Original Filed t- 1919 2 Sheets-Sheet 2 Patented SepLZl, 1926.

, .UNITED STATES I 1,500,316- P TENToFFICEQ CHARLES EDWARD CAMPBELL, OF LYNN, MASSACHUSETTS, ASSIGNOR, 'BY M'EsNE'As 'SIGNMENTS, 'ro LYNN COMMERCIAL REALTY 00., a CORPORATION on MASSAGHU:

ELECTRICAL SYSTEM.

Application filed October 23, 1919, Serial No. 332,733. Renewed Februray 10, 1926.

The present invention relates to electrical systems and more particularly to X-ray systems.

The use of X-rays fordiagnosis or radiography requires considerable skill and eX- perience. Among other prerequisites, all the adjustable parts must be exactly adjusted. In order to simplify the process, so that it may be performed by persons of ordinary skill, a number of short cuts have been proposed, among them a suggestion that all radiographs be taken with X-rays of the same degree of penetration At least one of the adjustments is thereby ordinarily rendered unnecessary and the process simplified to that extend. Though ideal conditions are not thereby attained, it is poss ble, byv suitable design, to reach a fair degree of approximation. V

\Vhen it is desired to maintain a constant current flow through the X-ray tube, the carrying out of this suggestion is comparatively easy, for all that is necessary is to subject the tube, terminals to a predeter m ned voltage. But not all objects can be satisfactorily radiographed with the same value of current flow through the tube.

An object of theinvention is to provide an improved X-ray system, the X-rays generated by which shall have substantially the same degree of penetration irrespective of variations in the value "of the current flowing through the tube. 7

As is well known,,certain types of X-ray tubes are adapted for the passage there through of current flowing in one direction only, andwill prevent the passage of current flowing in the opposite direction. If such a tube be directly connected to a source ofalternating-current energy, therefore, part of the current wave will be prevented from flowing through. The .alternating current suppl ed is thus rectified by the tube. The current which flows through is known as the useful current and the rest as the inverse current, and similarly with the voltages. The inverse voltage is thus naturally greater than the useful voltage and the difference between the two will vary with differences in the load. I

As the inverse, current and voltage produce noradiographic effect from the tube and as the degre e of penetration of the X'- rays and their volume are funct ons, re-

spectively, of the useful voltage across the tube terminals and the current flowing in the tube, it readily appears that the degree of penetration of the X-rays depends upon the useful voltage only and the volume of X-rays dependsupon the useful current only. The greater the useful current,.the greater will be the volume of K -rays emitted; but asan increased useful current naturally results in a. decreased useful voltage, the X-rays emitted will be of less penetrating character. Similarly, if the useful current be decreased, the useful voltage will naturally become increased, with the' result that. the Xerays emitted, though of smaller volume, will be more penetrating. To maintain the penetration constant, therefore, provisionmujst be made for increasing ordecreasing the useful voltage accordingly as the useful current is decreased orincreased.

'To'thefattainment ofthe, above-mentioned object, therefore, a feature of the invention resides in compensating for the changes in the useful voltage resulting from changes in the useful current, so that the useful voltage, and, therefore, the penetration of the Xrays, will remain substantially constant irrespective of changes in the useful current.

VVith the above and other objects in view, as will be apparent to persons skilled in the art, the invention consists in the improved X-ray' system hereinafterdescribed and defined in the appended claims.

In the accompanying drawings, Figure 1 is a diagrammatic view of an X-ray system embodying the invention; and Fig. 2

The invention'is illustrated in its preferred form in connection with an electronic X-ray tube and a high-potential transformer for exciting or generating X-rays in the tube, though it will be obvious that the invention is notlimited to any particular type of tube or any particular exciting means. As is well known, the value of the'current flowing in such a tube depends upon the degree of incandescence of the cathode filament. According to the preferredembodiment of the invention, therefore, the useful current is adjusted by adjusting ,the energy supplied to the filament. If the filament becomes more highly heated, for example, a greater useful current will flow through the tube, and a lower useful voltage across the tube terminals would naturally result. This would lower'the degree of penetration of the is a similar view of a modification. r

X-rays. Simultaneously with the increased heating of the filament, however, the voltage of the transformer is increased, which resultsinincreasing. the useful voltage across the tube terminals. This increase in the useful voltage compensates for the lowering in the useful voltage which would otherwise be caused by the increased heating of the filament. The useful voltage and, therefore, the penetration of the X-rays also, are thus maintained substantially constant.

In the preferred form of the invention which is illustrated in Fig, 1, the electronic type of tube is diagraimnatically shown at 2 and comprises an anode l and a cathode comprising; afilament 6. The anode is connected by a conductor 8 to an Xterior ter minal of the secondary winding 10 of a high-potential transformer 12. The cathode 6 is connected by a conductor 14 to the other'exterior terminal of the secondary winding 10. The secondary winding 10 is preferably composed of two elements, as shown, the interior terminals of which are grounded by conductors 1'6 and 18, respec tively, to a terminal 20 of the primary winding 22' of the transformer 12. By means of this arrangement of parts, the static strain between the tube terminals and the'ground is approximately evenly distributed; An ammeter 20 is preferably connected incircuit with the conductor 18. The winding 22'serves also as the primary winding of another transformer, the secondary winding of which is indicated at 26, and is composed of very few turns. 7 The winding 26 supplies the requisite energy for energizing; the filament 6 through the adjustable resistance 27;- The same w nding 22" which operates to excite r-rays in the tube therefore operates alsoto heat the filament. The winding 26 is grounded to the secondary winding 1'0 by the conductor 14.

,The terminal 20' of the primary winding 22is connected by a conductor 28 toa terminal 30 of auto-transformer 82: other terminal 3 2 of the primary winding 22' is connected-by a switch 36 and a switch 38* to the other terminal 420 of the autotransformer 32. The switch 38 serves to connect the terminal 3% to any one of a.

number of taps 42, 44 and 46 (three only being illustrated atithe terminal 40 of the auto-transformer and the switch 36 is employed to close the circuit afterthe switch 38' has been suitably adjusted, thereby preventing arcing uponthe switch 88.

The terminal" 30 of the autoetransformer 32 is connected by a: conductor 48, through a: knife switch 50, to a line conductor 52; Any oneof a: number of taps 54, of the auto transformer 32, may be connected, through a switch 56 and theswitch 50't0 a line cond'uctor 58-. The-line conductors 52' and; 58 are connected to: any suitable source of: al-

The

ternating-current energy,v not shown. A voltmeter 60 is connected across the termina-ls 30 and 40 of the auto-transformer 32, for indicating changes in" the voltage su-pplied to the auto-transformer from the line conductors 52 and'58. I

In operation, the switch 50 is first closed to connect the auto-transformer 82 to the line conductors 52 and 58'. Through suitable adjustment of the switch 56, the volt-.

38- and 36 are closed in this order and opened in the reverse order, the arcing caused by the making and breaking of the circuit will take place upon the switch 36 alone, protecting the switch 88.

The auto-transformer will now supply al ternating-current energy to the primary winding 22 of the higl'i-potential trans former 12 and energy will be; induced from the primary winding in the secondary windings 10 and 26, the winding IOsubjectin'g the tube terminals toa high voltage and the winding 26 supplying low voltage energy for heating the cathode filament 61 As explained above, one part of the current wave will be suppressed by the tubean'd unidirectional current only will flow in the tube. With this type of tube, therefore, the employment of a rectifier is unnecessary and the tube may therefore be directly conne'cted to the transformer 12, as shown. The current in the tube is knownasthe useful current and the corresponding voltage is known as the useful voltage; It will readily appear that the switch 56 affords a means for compensating for variations in the voltage of the source of energy, so that the tube may be operated at a constant use ful volt-age though the system may be connected tosources of energy of different voltage. @peration" of the tube at constant useful voltage is desirable when it is desired to employ Xi-rays of constant penetration. Not only'the useful voltage, but the useful current is also thus maintained constant, for, once the switch 56 has been: adjusted, the degree of incandescence of the filament is fixed, and it is the degree of incandes cence of the filament which determines the value of the useful current flowing: inthe tube. The useful current being" constant, the volume of X-ra-ys emitted is constant. X-rays of. constant penetration are thus emitted in cons-tant-ivolu1ne;.. Y

-"-.Though:it ispossible to employ X-rays ofconstant. penetration for radiographing a..:very large number ofobjects, the volume of the X-rays must be varied for some ob-. jects. For such objects, the useful-current must be changedthoughfif X-rays of the same penetrating quality are desired, the

useful voltage must be maintained; constant; The change in useful current may be ob-.

tained by changingwtherdegree of. incan descence of the filamentthrough suitable manipulation of the switch 38.; The energy supplied to the filament depends uponthe voltage of the filament winding '26,=thi's voltage in turn depends upon the voltage of the. primary winding 22 and this upon the former," and that it is desired to increase either constant or varying volume.

the value. of the useful current, the switch 38 will be positioned so as "to" connect the primary winding22 to the tap 42. The primary winding 22 will, 0f course, besubI- jected to an increased voltage, which will cause an increased voltage of the secondary winding26. This, in 'turn, will cause the filament 6 to glow more brightly, which will cause an increased current flow in the tube. By reason of this increased flow of useful current in the tube, the useful voltage across the tube terminals would become decreased. But'the winding 26 is controlled in accordance with the degree of energization of the same primary winding 22 which operates to excite X-rays in the tube, so that the increased voltage of the primary winding 22 will cause an increased voltage in the secondary winding 10. This increased voltage will compensate for the decrease which would otherwise take place in the useful voltage, so as to main tain the useful voltage constant. The penetration of the X-rays will thus be maintained substantially constant, but their volume will become increased. If the switch 38 be connected to the tap46, on the other hand, the volume of X-rays will become decreased while maintaining constant the penetration of the rays. In practice, the number of taps 42, 44 and 46 may be as large as desired to provide for fine adjustments of the volume While maintaining the penetration of the X-rays constant.

The present invention therefore provides for radiographing a large variety of objects with rays of constant penetration and The switch 56 and the voltmeter 6O afford a means for connecting the system to any desired source of energy so that rays of a predetermined, penetration may be obtained irrespective of variations 1 in the .energy of suchwsource and.:-.the switch. .38 affords a means for varying thev volume of therays without varying the predetermined penetratingsqualityoftl1e rays.--= .a.

.It will be not'edthat inthe systemof Fig. 1, the filament winding 26 and the. winding 10. become simultaneouslyuenergzed upon the closing of the switch 36.. The winding 10 immediately subjects the tube to axhi gh voltage. The. filament however, cannot become heated to 1 its {maximum degree Yuntil after'the-lapse or a time interval. -':Until the maximum temperatureof the filament attained, the current flowing :in the tube can not reach its required maximum, normal value. r

- l Vhile X-raysbf the desired penetrating quality are generated, therefore,they are not produced in the required volume until after the expirationot .the' time interval. Pro vision is accordingly made in the system-of Fig.9 'for'energizing the-filament prior to subj ecting' :the tube terminals to a-high voltage', sothat the filament may be permitted to reach its maximum degree o'f incan'descence-before any X-rays'are generated. fThe filament winding 26 offt'hi's system is the secondary winding of a-jtrans'f'ormer 62 separate and distinct from fth'e tra-nsformer 12;

and having a'separate primary win'ding 64'. One terminalfof the winding 64 isconnected to'the terminal 20 andtheotherterininal of the I winding 6 51's connected to the terminal 30 of the auto-transformer 5 32, through an adjustable resistor 66. The switch 38 is directly connected to the, terminal 20 by a conductor 68. A switch connects the terminal 34 of the primary winding 22. to the terminal 30- of the auto-transformer.

The switch 50 may be closed to connect the autotransformer to the source of energy and the switch 56 may be adjusted togive the proper reading of the voltmeter 60, as before, to provide for the generation of X-rays of constant penetration. If the switch 38 is connected to one of the taps 42, 44 and 46, the primary winding 64 of the filament transformer 62 will become immediately energized. The degree of energization of the winding 64 may be adjusted through the resistor 66. The transformer 12, however,

will remain deenergized until the closing of' taneous adjustment of the energy in the the filament transformers 12 and 62, so that the penetra tion of the rays may be maintained substantially constant, though their volume may be varied.

It will be understood that the invent-ion is not'restricted to the specific embodiments thereof which are herein illustrated and described, the principal claims are, therefore, broad in scope.

I claim:

I 1.7 An X-ray system having, in combination, an X-ray tube having a cathode and an anode, a transformer for exciting X-rays in the tube having primary and secondary windings, said secondary winding comprising two elements, each having a pair of terminals, a source of energy to which said primary winding and one terminal of each of said elements is connected, andmeans respectively connecting said other terminals to said cathode and said anode respectively. 7

2. An X-ray system having, in combination, an X-ray tube having an anode and a cathodecomprising a filament, a transformer for exciting X-rays in the tube having primary and secondary windings, said secondary winding comprising two elements, a terminal of one of which is connected to said cathode and a terminal of the other of which is connected to said anode, an auto-transformer, means connecting one terminal of said primary winding and the other terminals of saidv elements to one terminal of said auto-transformer, a switch adjustably connecting the other terminal of said primary winding to the other terminal ofgsaid auto-transformer, a winding. connected to said filament constituting the secondary windingof a transformer for-heating the filament, said primary winding constituting the primary winding alsorof said filaw ment+heating transformer, a source oflenergyfand a ,switch adjustably connecting said auto-transformer to said source.

'3. An X-ray system having, in combination, an X-ray-tube having an anode. and a cathode comprising a filament, a transformer forexciting X-rays .in the, tube having primary and secondary windings, said secondary winding comprising two, elements a terminal of one of which is connected tosaid, cathode and a terminal of the other of which is connected to said anode, anvauto-transforrn'er, a switch connecting one terminal of said primary winding to one terminalof said auto-transformer, a switch adjustably con- CHARLES EDWARD CAMPBELL-.7 

